As Drought Persists, Collaboration Seeks To Advance Technology That Helps Generate New Water Supply

A researcher at the University of California, Riverside’s Bourns College of Engineering has been awarded $300,000 from the National Science Foundation (NSF) to help advance water reuse technologies for drinking water supplies.

The project is in partnership with Orange County Water District (OCWD), which operates the Groundwater Replenishment System (GWRS), the world’s largest water purification system for indirect potable reuse. The research will compare the addition of chloramines—a group of compounds that are generated when chlorine and ammonia are mixed —to a treatment step that currently uses hydrogen peroxide and ultraviolet (UV) light. The researchers believe the alternative process will improve water quality and lower treatment costs, ultimately alleviating water shortage concerns in one of the most drought-stricken areas of the United States.

OCWD manages and protects the Orange County Groundwater Basin, which supplies 75 percent of the potable water supply for 2.4 million people in north and central Orange County. GWRS water is a primary source of replenishment for the basin and accounts for one-third of the water that is put into it annually. A joint project of OCWD and the Orange County Sanitation District, the GWRS purifies treated wastewater to produce 100 million gallons of high-quality drinking water every day, enough water for 850,000 residents annually.

While all wastewater must be treated before being released back into the environment, treated wastewater that is purified for potable use must undergo a stringent purification process along with rigorous monitoring and testing. The GWRS purifies wastewater using a three‐step advanced process consisting of microfiltration, reverse osmosis, and ultraviolet (UV) light with hydrogen peroxide. The end result is ultra-pure water that meets or exceeds state and federal drinking water standards.

The NSF project, led by Haizhou Liu, assistant professor of chemical and environmental engineering at UCR, and Kenneth Ishida, principal scientist at OCWD, will investigate the addition of another group of compounds—chloramines—to the third step of the process, which currently uses UV light and peroxide. Liu said that like hydrogen peroxide, chloramines can be activated by UV light to degrade trace organic contaminants in wastewater in a reaction called an advanced oxidation process (AOP). While chloramines are frequently used in other stages of water purification processes, such as disinfection, they have not yet been studied as oxidants in the presence of UV light.

“So far, little is known about the optimization of chloramine photolysis for water reuse applications, but the results of early studies in my lab suggest a very beneficial reaction that could be relevant to many water utilities,” Liu said. “In particular, we found that chloramines can generate highly reactive chemicals upon UV photolysis, but this only happens under certain chemical conditions.”

Liu said the university-industry collaboration serves as a model to develop efficient, cost-effective and sustainable water reuse technologies that will improve U.S. global competitiveness in this field.  While OCWD chemists and engineers will acquire fundamental knowledge that can be applied in their existing system, UCR undergraduate and graduate students will gain industrial experience that will support their future careers.

“OCWD has a long history of implementing innovative technologies to address water demand,” Ishida said.

“If successful, this project can both save photon energy cost at treatment facilities and improve the quality of recycled water for drinking purposes. Our ultimate goal in developing this technology is to alleviate the drought impact and protect human health,” Liu said.

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